Removal of bacteria from a liquid medium such as water, is generally not a problem when there is an adequate water purification system such as those normally found in the more developed areas of the world and particularly in the more populated areas of the world such as in and about large cities. In these instances, conventional mass disinfection techniques such as chlorination, ozonation, and ultraviolet treatment are effective. These mass techniques are not practical for small domestic applications such as for treatment of private well water.
It is known that macroreticular anion exchange resins are effective in removing bacteria from a liquid medium such as water or during processing of foods in a food plant. It is also known that such macroreticular anion exchange resins may have microbiocides physically or chemically bound thereto and that liquid media containing bacteria may be removed and destroyed using such ion exchange resins with microbiocides.
The use of ion exchange resins, with or without microbiocides, to remove bacteria from liquid media has been severally limited by the fact that there has been no way to determine when the capacity of the resin to remove bacteria has been exhausted. Thus removal of bacteria using such resins has been limited because, after the capacity of such resins to remove bacteria has been substantially exhausted, the liquid effluent from the ion exchange column will contain bacteria and this fact will normally be unknown to the user of such column.
British Pat. No. 1,107,768 is directed to a water purifying apparatus for removing pyrogens from a water supply so that the water, after treatment, can be used for medical purposes such as intravenous injections. The British Patent discloses an apparatus for purifying water which includes an ion exchange column and a membrane filter. The function of the ion exchange column is not stated but the aforesaid patent states that the function of the membrane filter is to protect the ion exchange resin and the effluent from micro-organisms present in the feed water. The British Patent fails to provide for any means whereby exhaustion of the ion exchange resin is indicated. In fact, the membrane filter is arranged so that the influent passes through the membrane filter prior to passing through the ion exchange resin.
An article entitled "Preparation of Biologically Pure Water By Ion Exchange"; Saunders et al; Ion Exchange in the Process Industry Conference; London Society of Chemical Industries; London; July 16-18, 1968; pages 410-415, discloses the purification of water to render it suitable for all purposes in medicine and pharmacy. This article teaches the removal of pyrogenic substances from water by passing the water through a pre-purifier mixed resin bed followed by passing the water through a macroreticular ion exchange resin and then through a series of submicron (0.22 micron) membrane filters.
This article fails to teach the necessity for a pressure tight connection between the ion exchange resin and the membrane filter. The article also states that the final membrane filter is not essential to give sterility but may be used as an additional precaution against micro-organisms and as a barrier to prevent resin fines from passing into the effluent.
This article and British Pat. No. 1,107,768 failed to recognize the necessity for an indicator to advise the user when the capacity of the ion exchange resin was exhausted.